MicroRNA-21 contributes to the puerarin-induced cardioprotection via suppression of apoptosis and oxidative stress in a cell model of ischemia/reperfusion injury

Puerarin, a major bioactive constituent of the Radix puerariae, can ameliorate myocardial ischemia/reperfusion (I/R) injury. Emerging evidence supports that microRNA (miR)-21 functions as a protective factor against I/R and/or hypoxia-reperfusion (H/R)-induced myocardial injury. However, the role of miR-21 in the cardioprotective effect of puerarin remains unclear. Therefore, the purpose of the present study was to demonstrate the involvement of miR-21 in the cardioprotective mechanisms of puerarin using a cell model of I/R injury, generated by culturing rat H9c2 cardiomyocytes under H/R conditions. The results demonstrated that pre-treatment with puerarin significantly increased cell viability, decreased lactate dehydrogenase activity and upregulated miR-21 expression in H/R-treated H9c2 cells. Transfection of an miR-21 inhibitor led to an increase in H/R-induced cytotoxicity and reversed the protective effects of puerarin. Additionally, miR-21 inhibition attenuated the puerarin-induced decrease in the rate of apoptosis, caspase-3 activity and the expression of apoptosis regulator Bax, and increased apoptosis regulator Bcl-2 expression, under H/R conditions. Furthermore, puerarin mitigated H/R-induced oxidative stress as evidenced by the decrease in endogenous reactive oxygen species production, malondialdehyde content and NADPH oxidase 2 expression, and enhanced the antioxidative defense system as illustrated by the increase in superoxide dismutase activity, catalase and glutathione peroxidase levels. These effects were all eliminated by miR-21 inhibitor transfection. Furthermore, the miR-21 inhibitor exacerbated the H/R-induced oxidative stress and attenuated the antioxidative defense system in H/R-treated H9c2 cells. Taken together, the results suggested that miR-21 mediated the cardioprotective effects of puerarin against myocardial H/R injury by inhibiting apoptosis and oxidative stress.